1. Field of the Invention
The present invention relates to solid-state storage subsystems. More specifically, the present invention relates to providing data redundancy within a solid-state storage subsystem.
2. Description of the Related Art
Companies are increasingly relying on portable solid-state storage subsystems to persistently store executable code and data. Typically, these subsystems are in the form of a memory card or drive that connects to an external port or connector of a host computer system. Because solid-state storage subsystems tend to be lighter, smaller and more shock resistant than magnetic disk drives, they are especially useful for applications involving portability. In many cases, the solid-state storage subsystem is used by the host system as a boot device (i.e., it stores the operating system code executed by the host computer), and/or is used to persistently store data generated or captured by the host computer.
One problem with existing solid-state storage subsystems is that they typically do not provide a sufficient degree of protection against data losses. Such data losses are typically caused by memory wear, memory array controller malfunctions, or rampant host software that overwrites important data. When such data losses occur, they can result in significant down time and lost revenue, especially if the storage subsystem is used to store operating system files or critical data.
The present invention comprises a storage subsystem which contains multiple non-volatile memory arrays that are accessible to a host system when the storage subsystem is connected thereto. The storage subsystem implements commands and/or modes for enabling the host system to create and use backup copies of files, such that the host system can recover when files become corrupted or otherwise lost. In one embodiment, the storage subsystem presents the non-volatile memory arrays to the host's operating system as distinct storage devices (e.g., ATA device 0 and 1), and implements special commands for copying data between these disk drives. The subsystem may alternatively present the memory arrays to the host operating system as a single storage device. The storage subsystem may have a standard form factor, such as a form factor commonly used for memory cards.
Specific embodiments of the invention will now be described with reference to the following drawings:
Specific embodiments of the invention will now be described with reference to the drawings. This description is intended to illustrate example implementations of, and applications for, the present invention, and is not intended to be limiting. Nothing in this description is intended to imply that any particular feature, characteristic, or mode of operation is a requirement of the invention. The invention is defined by the claims.
The host system 110 executes a special driver 113 or other software component that communicates with the subsystem 112 using the subsystem's command set. As discussed below, this command set preferably includes both standard ATA commands, and non-standard or “vendor-specific” commands for performing various types of data backup and restore operations. The subsystem 112 may also be used with hosts that do not execute special driver software (i.e., a standard operating system driver may be used), although the subsystem's non-standard backup and restore operations will not be available to the host in such configurations.
In the illustrated embodiment, the first NVM array 116 is controlled primarily by a first controller 114, and the second NVM array 117 is controlled primarily by a second controller 115. However, in other embodiments, both NVM arrays 116, 117 may be controlled exclusively by a single controller. Where two controllers 114 and 115 are provided as shown, each controller/memory array pair preferably appears to the host system 110 as a separate ATA disk drive, with one configured as device 0 (the “master”) and the other as device 1 (the “slave”). Thus, the host system 110 can selectively write data to, and read data from, each of the NVM arrays 116 and 117 using standard ATA disk drive commands. More specifically, each controller 114 and 115 is configured to write data to, and read data from, its respective the NVM array 116 and 117 in response to commands from the host system 110.
The design shown in
Although two NVM arrays are used in the embodiment of
Referring again to
As further illustrated in
The storage subsystem 112 comprises a physical connector 150 for detachably connecting to the host 110. The connector 150 and associated signal interface preferably comply with an industry-standard such as a USB, SATA (Serial ATA), PC Card/PCMCIA, PCI Express, Firewire (IEEE 1394), Parallel ATA (PATA), CompactFlash (CF), Secure Digital (SD), or Memory Stick (among others). The subsystem 112 may alternatively be designed to communicate with the host 110 via a wireless interface, such as a Bluetooth interface, or via a non-standard interface.
Although not separately illustrated in
As will be apparent, the storage subsystem 112 provides data redundancy features that are typically available only in relatively large systems, such as disk array systems containing multiple magnetic disk drives. Unlike conventional disk array systems, however, the storage subsystem 112 can advantageously be implemented as a highly compact device that does not require any cabling, and that is powered by the host 110 via the same standard connection used for data. For example, the storage subsystem 112 can be implemented as a PCMCIA, CF or SD card or as a USB flash drive.
The two controllers 114 and 115 may be identical to each other. Each may be provided as separate integrated circuit, or both may be integrated within a common integrated circuit. As illustrated, each includes a respective buffer 152 (implemented in volatile RAM) for buffering data being written to or read from non-volatile memory, and includes interface circuitry 154 for implementing the appropriate signal interface for communicating with the host. The controllers 114 and 115 are preferably capable of executing firmware, although the functions embodied firmware may alternatively be implemented in state machine logic. In addition to implementing the ATA specification, the controllers 114, 115 may be capable of executing USB commands, PC Card commands, or CF commands, or commands associated with another specification.
The NVM arrays 116, 117 may be implemented using NAND memory devices, NOR memory devices, and/or any other type of solid-state non-volatile memory device. The solid-state memory devices may be physically divided into blocks, pages and sectors, as is known in the art.
To facilitate use of the dual NVM arrays to protect against losses, the storage subsystem 112 preferably implements two special modes, referred to as “mirror mode” and “switch device mode.” The subsystem 112 may be placed in one of these modes via a vendor-specific “mode set” command, the general format of which is shown in
As discussed in the following section, the storage subsystem also preferably implements a set of special (vendor-specific) commands for mirroring, backing up and restoring blocks of data. It should be understood that the particular modes and commands described herein are merely illustrative, and are not required to practice the invention. For example, in embodiments in which three of more separate NVM arrays are provided, a very different set of special modes and/or commands will typically be used.
When in mirror mode, the storage subsystem 112 writes to both NVM arrays 116, 117 when a standard write command is issued by the host. This mode may advantageously be used to efficiently mirror important files across the two NVM arrays/ATA devices. For example, a host system could initially place the subsystem in mirror mode, then write a set of OS (operating system) files, or other important files, to either device 0 or device 1 via standard ATA write commands. This would cause these files to be written to both devices/arrays, such that a backup copy is available if, for example, one copy becomes corrupted. As discussed below, mirrored copies of files can also be created using the mirror command.
The mirror mode is preferably implemented by having each controller 114, 115 perform a write to its respective NVM array whenever a standard write command is received, regardless of whether this command is directed to device 0 or device 1. Alternatively, the controller to which the write command is directed could write the data to both NVM arrays.
In some embodiments, the storage subsystem may also implement an “address constrained” mirror mode in which only those writes falling within a particular address range or zone are mirrored. For example, a particular zone may be created in one of the NVM arrays for storing mission critical data, and all writes to this zone may automatically be mirrored to a corresponding zone of the other NVM array. The storage subsystem 112 may create such zones in response to host command as disclosed in U.S. patent application Ser. No. 11/480,303, filed on Jun. 30, 2006, the disclosure of which is hereby incorporated by reference.
When in “switch device” mode, the storage subsystem 112 switches the designations of device 0 and device 1 as recognized by the host system 110 for purposes of all read and write commands. Thus, if the host 110 issues a read or write command to device 0, the command will actually be handled by device 1 (and vice versa). This mode may be used to facilitate recovery after a failure or data loss. For example, if the host ordinarily boots from device 0 but is failing to do so (e.g., because the OS files on device 0 have become corrupted), and the OS files are also stored on device 1, the host/driver may place the subsystem 112 in the switch device mode prior to the next boot attempt. This advantageously causes the host to boot from device 1 without the need to modify the host's BIOS.
The switch device mode may also be used in other contexts. For instance, the host 110 may place the storage subsystem 112 in “switch device” mode (to cause the host to subsequently boot or otherwise execute from device 1) upon detecting that NVM array 0 is close to the end of its useful life. This determination may be made by reading out usage/wear-level statistics maintained by the storage subsystem, as disclosed in U.S. patent application Ser. No. 11/429,936, filed on May 8, 2006, the disclosure of which is hereby incorporated by reference. As another example, each controller 114, 115 may be capable of detecting, and reporting to the host, when an unusually high number of ECC or parity errors are occurring on reads from its respective NVM array; and the host may respond by placing the subsystem in “switch device” mode during a subsequent boot up.
In some embodiments, the storage subsystem 112 may include a device selector 121 (
The device selector 121 advantageously allows the subsystem 112 to be placed in the “switch device” mode regardless of whether the subsystem is being used with a host capable of issuing vendor-specific commands. For instance, a user may experience a boot error while using the subsystem with a host system that does not have the subsystem's driver 113 or other special software installed thereon, and which is therefore incapable of sending a “switch device” command to the subsystem. In response to encountering the boot error, the user could use the device selector 121 to activate the “switch device” mode and then restart the host system 110.
In the embodiment shown in
The Backup All command directs the subsystem 112 to internally back up the entire contents of NVM array 0 (or a particular zone thereof, as discussed below) to NVM array 1. Any data that is stored in NVM array 1 (or the target zone thereof) is erased or overwritten during this process. This command may be used to efficiently set a recovery point in case of a failure. For example, a host system 110 that has been updating critical files in the storage subsystem 112 may issue a Backup All command to cause the device 0 controller 114 to copy some or all of the files in NVM array 0 to NVM array 1.
In some embodiments, the Backup All command may specify a particular zone to be backed up. In these scenarios, only the files stored in the specified zone of device 0 are copied to device 1. The zones may be created using vendor-specific commands as described in application Ser. No. 11/480,303, referenced above. For example, NVM array 0 can be divided into two zones, zone 1 and zone 2, with only zone 1 being used to store critical data. Rather than backing up all contents of NVM array 0, the backup operation can then be limited to zone 1.
The Restore All command directs the storage subsystem 112 to internally copy the entire contents of NVM array 1 (or a designated zone thereof) to NVM array 0. Any data that is stored in NVM array 0 (or the target zone thereof) is erased or overwritten during this process. This command may be used to restore files on device 0 that have become corrupted. For example, if the host system 110 has crashed due to possible corruption of OS files on device 0, and has previously created a backup copy on device 1, the host may issue a Restore All command to the storage subsystem 112 and then attempt to re-boot from device 0.
The Mirror command is the same as a standard write command, except that the storage subsystem 112 writes the data (via the respective controllers 114, 115) to both NVM arrays 116, 117. This command may be used in place of the mirror mode to create a backup copy of data being written to device 0, particularly when the quantity of data being backed up is small.
The backup command causes the subsystem 112 to internally read a designated set of sectors of device 0, and to write (back up) the read-out data to device 1. This command may be used in place of a Backup All command when the quantity of data being backed up is relatively small.
The Restore Command causes the subsystem to read a designated set of sectors in device 1, and to write the data read from these sectors to a corresponding set of sectors in device 0. This command may be used when, for example, the host detects that data stored in a particular sector or set of sectors of device 0 has likely become corrupted.
Each of the N flash disk controllers 516 communicates with a master controller 520. For example, as the master controller 520 receives read and write commands from the host 110 (which may be ATA commands, PC Card commands, USB commands, etc.), the master controller translates these commands into drive-specific ATA commands that are sent to the corresponding flash disk controllers 516. Data read by the flash disk controllers 514 is transferred to the master controller's buffer 525 before being transferred to the host 110. The master controller 520 includes interface circuitry 522 for communicating with the host 110 in accordance with one or more interface standards (as described above).
The master controller also includes a mode register 524 for enabling the host to specify a particular mode and configuration. The following are examples of modes that may be implemented.
As with the embodiment of
RAID array. When in this mode, the storage subsystem 512 effectively treats each NVM array 514 as a respective disk drive of a disk array, and operates the disk array in an appropriate RAID (Redundant Array of Inexpensive Disks) configuration. Depending on the value of N, one of the following RAID configurations (as well as others) may be used: RAID 0, 1, 2, 3, 4, 5, 6, 7, 0+1, or 10. The RAID array may be presented to the host 110 as a single virtualized disk drive.
The flash disk controllers 516 and the master controller 520 collectively form the main components of a flash disk array controller 530. The flash disk array controller 530 may be implemented as a single IC device or as multiple IC devices.
The storage subsystem 512 shown in
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to be limiting. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms, including forms that do not provide all of the features and benefits described herein. Furthermore, various omissions, substitutions and changes in the form of the disclosed methods and systems may be made without departing from the invention. The invention is defined by the accompanying claims.
Number | Name | Date | Kind |
---|---|---|---|
4296464 | Woods | Oct 1981 | A |
4937736 | Chang et al. | Jun 1990 | A |
5018096 | Aoyama | May 1991 | A |
5442768 | Sudoh | Aug 1995 | A |
5721873 | Tobita et al. | Feb 1998 | A |
5737563 | Shigeeda | Apr 1998 | A |
5740397 | Levy | Apr 1998 | A |
5768612 | Nelson | Jun 1998 | A |
5784698 | Brady et al. | Jul 1998 | A |
5890219 | Scaringella et al. | Mar 1999 | A |
6000006 | Bruce et al. | Dec 1999 | A |
6014727 | Creemer | Jan 2000 | A |
6052799 | Li et al. | Apr 2000 | A |
6081878 | Estakhri et al. | Jun 2000 | A |
6088765 | Ohtsuka | Jul 2000 | A |
6092095 | Maytal | Jul 2000 | A |
6134631 | Jennings, III | Oct 2000 | A |
6173360 | Beardsley et al. | Jan 2001 | B1 |
6223252 | Bandera et al. | Apr 2001 | B1 |
6249838 | Kon | Jun 2001 | B1 |
6269434 | Tanaka | Jul 2001 | B1 |
6272589 | Aoki | Aug 2001 | B1 |
6286087 | Ito et al. | Sep 2001 | B1 |
6324627 | Kricheff et al. | Nov 2001 | B1 |
6401214 | Li | Jun 2002 | B1 |
6434648 | Assour et al. | Aug 2002 | B1 |
6452950 | Ohlsson et al. | Sep 2002 | B1 |
6484229 | Ichikawa et al. | Nov 2002 | B1 |
6530034 | Okada et al. | Mar 2003 | B1 |
6546456 | Smith et al. | Apr 2003 | B1 |
6564173 | Arntz et al. | May 2003 | B1 |
6633963 | Ellison et al. | Oct 2003 | B1 |
6675281 | Oh et al. | Jan 2004 | B1 |
6694381 | Lo et al. | Feb 2004 | B1 |
6704012 | Lefave | Mar 2004 | B1 |
6732221 | Ban | May 2004 | B2 |
6735636 | Mokryn et al. | May 2004 | B1 |
6754765 | Chang et al. | Jun 2004 | B1 |
6761580 | Chang | Jul 2004 | B2 |
6792519 | Constable et al. | Sep 2004 | B2 |
6871272 | Butterworth | Mar 2005 | B2 |
6892248 | Thayer | May 2005 | B2 |
6944063 | Chen et al. | Sep 2005 | B2 |
6944717 | Yoneyama et al. | Sep 2005 | B2 |
6968434 | Kamano et al. | Nov 2005 | B2 |
6976190 | Goldstone | Dec 2005 | B1 |
6978398 | Harper et al. | Dec 2005 | B2 |
6996623 | Kawano et al. | Feb 2006 | B1 |
7024410 | Ito et al. | Apr 2006 | B2 |
7054986 | Zhao et al. | May 2006 | B2 |
7079395 | Garnett et al. | Jul 2006 | B2 |
7103798 | Morita | Sep 2006 | B2 |
7114051 | Guu et al. | Sep 2006 | B2 |
7139871 | Mizuno | Nov 2006 | B2 |
7139890 | Moran et al. | Nov 2006 | B2 |
7210013 | Itoh et al. | Apr 2007 | B2 |
7213117 | Wakabayashi et al. | May 2007 | B2 |
7262961 | Motoe et al. | Aug 2007 | B2 |
7277978 | Khatami et al. | Oct 2007 | B2 |
7447807 | Merry et al. | Nov 2008 | B1 |
7447944 | Hu | Nov 2008 | B2 |
7464306 | Furuhjelm et al. | Dec 2008 | B1 |
7467258 | Murayama | Dec 2008 | B2 |
7509441 | Merry et al. | Mar 2009 | B1 |
7596643 | Merry, Jr. et al. | Sep 2009 | B2 |
7653778 | Merry et al. | Jan 2010 | B2 |
7684417 | Imai et al. | Mar 2010 | B2 |
7694188 | Raghuraman et al. | Apr 2010 | B2 |
7765373 | Merry et al. | Jul 2010 | B1 |
7912991 | Merry et al. | Mar 2011 | B1 |
7962792 | Diggs et al. | Jun 2011 | B2 |
8078918 | Diggs et al. | Dec 2011 | B2 |
8122185 | Merry, Jr. et al. | Feb 2012 | B2 |
8127048 | Merry et al. | Feb 2012 | B1 |
8151020 | Merry, Jr. et al. | Apr 2012 | B2 |
20020138602 | Vinberg | Sep 2002 | A1 |
20030069671 | Yashiki et al. | Apr 2003 | A1 |
20030131093 | Aschen et al. | Jul 2003 | A1 |
20030188007 | Unger | Oct 2003 | A1 |
20030200388 | Hetrick | Oct 2003 | A1 |
20030227451 | Chang | Dec 2003 | A1 |
20040128414 | Rudelic | Jul 2004 | A1 |
20040145952 | Chen et al. | Jul 2004 | A1 |
20040190877 | Matsuno et al. | Sep 2004 | A1 |
20040210796 | Largman et al. | Oct 2004 | A1 |
20040228197 | Mokhlesi et al. | Nov 2004 | A1 |
20040246841 | Miyamoto | Dec 2004 | A1 |
20040260967 | Guha et al. | Dec 2004 | A1 |
20050036387 | Seal et al. | Feb 2005 | A1 |
20050044454 | Moshayedi | Feb 2005 | A1 |
20050047396 | Helm et al. | Mar 2005 | A1 |
20050138306 | Panchbudhe et al. | Jun 2005 | A1 |
20050160195 | Bruner et al. | Jul 2005 | A1 |
20050196165 | Dybsetter et al. | Sep 2005 | A1 |
20050197017 | Chou et al. | Sep 2005 | A1 |
20050210098 | Nakamichi et al. | Sep 2005 | A1 |
20050268007 | Nakabayashi | Dec 2005 | A1 |
20050281112 | Ito et al. | Dec 2005 | A1 |
20050289275 | Jung et al. | Dec 2005 | A1 |
20060056813 | Sutardja | Mar 2006 | A1 |
20060069866 | Miyazaki | Mar 2006 | A1 |
20060085670 | Carver et al. | Apr 2006 | A1 |
20060085836 | Lyons, Jr. et al. | Apr 2006 | A1 |
20060095647 | Battaglia et al. | May 2006 | A1 |
20060095699 | Kobayashi et al. | May 2006 | A1 |
20060143426 | Wu | Jun 2006 | A1 |
20060159098 | Munson et al. | Jul 2006 | A1 |
20060179218 | Burkey | Aug 2006 | A1 |
20060190696 | Ito et al. | Aug 2006 | A1 |
20060200627 | Iftikar | Sep 2006 | A1 |
20060212750 | Denninghoff et al. | Sep 2006 | A1 |
20060248387 | Nicholson et al. | Nov 2006 | A1 |
20060282709 | Shu et al. | Dec 2006 | A1 |
20060294338 | Fisher et al. | Dec 2006 | A1 |
20070008186 | Michaels et al. | Jan 2007 | A1 |
20070053513 | Hoffberg | Mar 2007 | A1 |
20070073944 | Gormley | Mar 2007 | A1 |
20070079097 | Karnowski et al. | Apr 2007 | A1 |
20070124130 | Brunet et al. | May 2007 | A1 |
20070124542 | Ven | May 2007 | A1 |
20070159710 | Lucas et al. | Jul 2007 | A1 |
20070180328 | Cornwell et al. | Aug 2007 | A1 |
20070201814 | Yamauchi | Aug 2007 | A1 |
20070260811 | Merry et al. | Nov 2007 | A1 |
20070266200 | Gorobets et al. | Nov 2007 | A1 |
20070268791 | Grow et al. | Nov 2007 | A1 |
20070283090 | Kaji et al. | Dec 2007 | A1 |
20080046766 | Chieu et al. | Feb 2008 | A1 |
20080109591 | Kim et al. | May 2008 | A1 |
20080294669 | Narayanan | Nov 2008 | A1 |
20090037643 | Ohtsuka et al. | Feb 2009 | A1 |
20090063895 | Smith | Mar 2009 | A1 |
20100011260 | Nagadomi et al. | Jan 2010 | A1 |
20100023800 | Harari et al. | Jan 2010 | A1 |
20120151130 | Merry, Jr. et al. | Jun 2012 | A1 |
Number | Date | Country |
---|---|---|
0 589 597 | Mar 1994 | EP |
05-100801 | Apr 1993 | JP |
2006118646 | Sep 2006 | WO |
Entry |
---|
Andrew S. Tanenbaum, “Structured Computer Organization”, 1984, Prentice-Hall, Inc., 3rd edition, pp. 11-13. |
Webpage printed out from <http://www.m-systems.com/site/en-US/Support/DeveloperZone/Software/LifespanCalc.htm> on Jun. 13, 2006. |
Webpage printed out from <http://www.m-systems.com/site/en-US/Technologies/Technology/TrueFFS—Technology.htm> on Jun. 13, 2006. |
Webpage printed out from <http://www.techworld.com/storage/features/index.cfm?FeatureID=498> on Jun. 13, 2006. |
International Search Report and Written Opinion in PCT Application No. PCT/US2007/68490; Dated Sep. 29, 2008 in 11 pages. |
Document explaining prior sale. |
Silicondrive User'S Guide, SiSMART Function, Preliminary Version 2.2 Revision A, Feb. 2005. |
International Search Report and Written Opinion for International Application No. PCT/US09/32984, mailed on Mar. 17, 2009, in 10 pages. |
International Search Report and Written Opinion for International Application No. PCT/US09/33262, mailed on Mar. 25, 2009, in 10 pages. |
SFF Committee Specification, “Self-Monitoring, Analysis and Reporting Technology (SMART) SFF-8035i Revision 2.0”, Apr. 1, 1996 in 24 pages. |
European Search Report dated Dec. 22, 2011 received in European Application No. 07762018.5 in 10 pages. |
Number | Date | Country | |
---|---|---|---|
20080147962 A1 | Jun 2008 | US |